Alkaline electrochemical cells comprising increased zinc oxide levels

ABSTRACT

Alkaline electrochemical cells are provided, wherein dissolved zinc oxide or zinc hydroxide is included at least in the free electrolyte solution, and/or solid zinc oxide or zinc hydroxide is included in the anode, so as to slow formation of a zinc oxide passivation layer on a zinc electrode. Methods for preparing such cells are also provided.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.62/795,750, filed Jan. 23, 2019, the contents of which are herebyincorporated by reference in their entirety.

BACKGROUND

Alkaline electrochemical cells are commercially available in cell sizescommonly known as LR6 (AA), LRO3 (AAA), LR14 (C) and LR20 (D). The cellshave a cylindrical shape that must comply with the dimensional standardsthat are set by organizations such as the International ElectrotechnicalCommission. The electrochemical cells are utilized by consumers to powera wide range of electrical devices, for example, clocks, radios, toys,electronic games, film cameras generally including a flashbulb unit, aswell as digital cameras. Such electrical devices possess a wide range ofelectrical discharge conditions, such as from low drain to relativelyhigh drain. Due to the increased use of high drain devices, such asdigital cameras, it is desirable for a manufacturer to produce a batterythat possesses desirable high drain discharge properties.

As the shape and size of the batteries are often fixed, batterymanufacturers must modify cell characteristics to provide increasedperformance. Attempts to address the problem of how to improve abattery's performance in a particular device, such as a digital camera,have usually involved changes to the cell's internal construction. Forexample, cell construction has been modified by increasing the quantityof active materials utilized within the cell.

Zinc (Zn) is a well-known substance commonly used in electrochemicalcells, such as dry cell batteries, as an active anode material. Duringdischarge of electrochemical cells, the zinc is oxidized to form zincoxide (ZnO). This zinc oxide reaction product forms a passivation layer,which can inhibit the efficient discharge of the remaining zinc,decreasing battery performance.

It is in an effort to overcome the limitations of the above-describedcells, and other such cells, that the present embodiments were designed.

BRIEF SUMMARY

An embodiment is an alkaline electrochemical cell, comprising:

a) a container; and

b) an electrode assembly disposed within the container and comprising acathode, an anode, a separator located between the cathode and theanode, and a free electrolyte solution;

wherein the anode comprises 1) solid zinc and 2) solid zinc oxide orsolid zinc hydroxide; and

wherein the free electrolyte solution comprises dissolved zinc oxide ordissolved zinc hydroxide.

BRIEF SUMMARY OF THE DRAWINGS

FIG. 1 is a cross-sectional elevational view of an alkalineelectrochemical cell of an embodiment.

FIGS. 2A and 2B are photographs of a control anode and an anodeaccording to an embodiment described herein, respectively.

FIGS. 3A and 3B are close-ups of the photographs in FIGS. 2A and 2B,respectively.

DETAILED DESCRIPTION AND DISCUSSION

Various embodiments now will be described more fully hereinafter withreference to the accompanying drawings, in which some, but not allembodiments are shown. Indeed, various embodiments may be embodied inmany different forms and should not be construed as limited to theembodiments set forth herein; rather, these embodiments are provided sothat this disclosure will satisfy applicable legal requirements. Likenumbers refer to like elements throughout. In the following description,various components may be identified as having specific values orparameters, however, these items are provided as exemplary embodiments.Indeed, the exemplary embodiments do not limit the various aspects andconcepts of the embodiments as many comparable parameters, sizes,ranges, and/or values may be implemented. The terms “first,” “second,”and the like, “primary,” “exemplary,” “secondary,” and the like, do notdenote any order, quantity, or importance, but rather are used todistinguish one element from another. Further, the terms “a,” “an,” and“the” do not denote a limitation of quantity, but rather denote thepresence of “at least one” of the referenced item.

Each embodiment disclosed herein is contemplated as being applicable toeach of the other disclosed embodiments. All combinations andsub-combinations of the various elements described herein are within thescope of the embodiments.

It is understood that where a parameter range is provided, all integersand ranges within that range, and tenths and hundredths thereof, arealso provided by the embodiments. For example, “5-10%” includes 5%, 6%,7%, 8%, 9%, and 10%; 5.0%, 5.1%, 5.2% . . . 9.8%, 9.9%, and 10.0%; and5.00%, 5.01%, 5.02% . . . 9.98%, 9.99%, and 10.00%, as well as, forexample, 6-9%, 5.1%-9.9%, and 5.01%-9.99%.

As used herein, “about” in the context of a numerical value or rangemeans within ±10% of the numerical value or range recited or claimed.

As used herein, “full cell electrolyte mass” refers to the total mass ofelectrolyte in the cell, and “full cell electrolyte concentration”refers to the total concentration of electrolyte in the cell. The fullcell electrolyte concentration can be found according to the calculation(full cell electrolyte mass)/(full cell electrolyte mass+total watermass in cell) multiplied by 100 if it is to be conveyed as a percentage.The total additive weight percent in the full cell electrolyte solutioncan be determined via the calculation (total mass of additive incell)/(total mass of additive in cell+full cell electrolyte mass+totalwater mass in cell)×100.

As used herein, the “total weight percent” of a zinc compound in a cell,or portion thereof, refers to the total weight of the zinc compound,compared to the total mass or weight of the zinc compound, electrolyte,and water in the cell or portion thereof. For example, “total zinc oxideweight percent” of a cell is calculated as (zinc oxide mass)/(zinc oxidemass+electrolyte mass+water mass)×100%.

“Total dissolved zinc oxide weight percent” in the full-cell electrolyteis calculated as (dissolved zinc oxide mass in cell)/(dissolved zincoxide mass in cell+electrolyte mass in cell+water mass in cell)×100%.This measurement does not account for the mass of solid (i.e.,undissolved) zinc oxide in the anode.

As used herein, the “electrolyte concentration percent” of an electroderefers to the total weight of the electrolyte in the electrode, comparedto the total weight of the electrolyte and the water in the electrode.For example the “KOH weight percent” of an electrode is calculated as(KOH mass in electrode)/(KOH mass in electrode+water mass inelectrode)×100%.

As used herein, “improvement” with respect to specific capacity meansthat the specific capacity is increased. Generally, an “improvement” ofa property or metric of performance of a material or electrochemicalcell means that the property or metric of performance differs (comparedto that of a different material or electrochemical cell) in a mannerthat a user or manufacturer of the material or cell would find desirable(i.e. costs less, lasts longer, provides more power, more durable,easier or faster to manufacture, etc.).

As used herein, “specific capacity” refers to the total amount of chargein an electrochemical cell when discharged at a particular rate. This istypically measured in ampere hours.

As used herein, “run-time” refers to the length of time that anelectrochemical cell will be able to provide a certain level of charge.

As used herein, describing a solution as “X % saturated” with a solutemeans that the solution comprises as a solute X % of the maximum amountof the solute that could be dissolved in the solution at the sametemperature, pressure, etc, accounting for all other components of thesolution (such as, for example, dissolved electrolyte).

Describing an electrochemical cell as having “X % total cell saturation”of a compound accounts for both the compound dissolved in freeelectrolyte solution as well as the presence of that compound in theanode. For example, in calculating the total cell saturation of zincoxide of an electrochemical cell, the amount of zinc oxide dissolved inthe free electrolyte solution would need to be determined, along withsolid and dissolved zinc oxide in the anode. This may result in a totalcell saturation percentage over 100%.

As used herein, a “source of zincate ions” refers to any compound whichproduces zincate ions (Zn(OH)₄ ²⁻) when placed in solution. Non-limitingexamples include Zn, zinc oxide (ZnO), and zinc hydroxide (Zn(OH)₂). Inan embodiment, the term may refer to only ZnO and Zn(OH)₂.

An embodiment is an alkaline electrochemical cell, comprising:

a) a container; and

b) an electrode assembly disposed within the container and comprising acathode, an anode, a separator located between the cathode and theanode, and a free electrolyte solution;

wherein the anode comprises 1) solid zinc and 2) solid zinc oxide orsolid zinc hydroxide; and

wherein the free electrolyte solution comprises dissolved zinc oxide ordissolved zinc hydroxide.

In an embodiment, the anode comprises solid zinc oxide and the freeelectrolyte solution comprises dissolved zinc oxide.

In an embodiment, the free electrolyte solution comprises dissolved zincoxide in an amount of greater than 2.0 weight percent. In a furtherembodiment, the free electrolyte solution comprises dissolved zinc oxidein an amount of about 4.0-6.5 weight percent.

In an embodiment, the anode comprises a gelled electrolyte, wherein thegelled electrolyte is prepared by combining a gelling agent with a firstaqueous alkaline electrolyte solution, wherein the first aqueousalkaline electrolyte solution comprises an alkaline metal hydroxideelectrolyte and dissolved zinc oxide. In a further embodiment, the firstaqueous alkaline electrolyte solution comprises dissolved zinc oxide inan amount of ≥2.5, ≥2.6, ≥2.7, ≥2.8, ≥2.9, ≥3.0, ≥3.1, ≥3.2, ≥3.3, ≥3.4,≥3.5, ≥3.6, ≥3.7, ≥3.8, ≥3.9, or ≥4.0 weight percent. In an embodiment,the first aqueous alkaline electrolyte solution comprises dissolved zincoxide in an amount of about 2.7-3.3 weight percent.

In an embodiment, the cathode comprises a second aqueous alkalineelectrolyte solution, wherein the second aqueous alkaline electrolytesolution comprises an alkaline metal hydroxide electrolyte and dissolvedzinc oxide. In a further embodiment, the second aqueous alkalineelectrolyte solution comprises dissolved zinc oxide in an amount of≥2.5, ≥2.6, ≥2.7, ≥2.8, ≥2.9, ≥3.0, ≥3.1, ≥3.2, ≥3.3, ≥3.4, ≥3.5, ≥3.6,≥3.7, ≥3.8, ≥3.9, or ≥4.0 weight percent. In a further embodiment, thesecond aqueous alkaline electrolyte solution comprises dissolved zincoxide in an amount of about 2.5-4.0 weight percent, or about 2.7-3.3weight percent.

In an embodiment, the first aqueous alkaline electrolyte solution andthe second aqueous alkaline electrolyte solution are identical.

In an embodiment, the total dissolved zinc oxide weight percent in theelectrochemical cell's full cell electrolyte solution is about 1.5-4.5weight percent. In an embodiment, the total zinc oxide weight percent inthe electrochemical cell's full cell electrolyte solution is about2.0-4.0 or about 2.5-3.5 weight percent. In an embodiment, the totalzinc oxide weight percent in the electrochemical cell's full cellelectrolyte solution is greater than about 4.5 weight percent. In anembodiment, the total zinc oxide weight percent in the electrochemicalcell's full cell electrolyte solution is about 0.5-4.5 weight percent,or about 0.5-3.0 weight percent, or about 0.5-2.0 weight percent.

In an embodiment, the electrochemical cell's full cell electrolyte isgreater than 40% saturated with dissolved zinc oxide.

In an embodiment, the solid zinc oxide or solid zinc hydroxide is asubstituted solid zinc oxide is substituted and comprises a cationsubstituent or an anion substituent, wherein the substituted solid zincoxide or substituted solid zinc hydroxide is less soluble thanunsubstituted solid zinc oxide or substituted solid zinc hydroxide.

In an embodiment, the substituted solid zinc oxide has the formulaZn_(1-x)Y_(x)O, wherein Y is at least one cation substituent, and0<x≤0.50.

In an embodiment, the substituted solid zinc hydroxide has the formulaZn_(1-x)Y_(x)(OH)₂, wherein Y is at least one cation substituent, and0<x≤0.50.

In an embodiment, the substituted solid zinc oxide has the formulaZnO_(1-w)A_((2w/z)), wherein A is at least one anion substituent,0<w≤0.50, and z is the charge of the anion substituent.

In an embodiment, the substituted solid zinc hydroxide has the formulaZn(OH)_(2-w)A_((w/z)), wherein A is at least one anion substituent,0<w≤0.50, and z is the charge of the anion substituent.

In an embodiment, the substituted solid zinc oxide has the formulaZn_(1-x)Y_(x)O_(1-w)(OH)_(2w), wherein Y is at least one cationsubstituent, wherein 0<x≤0.50, and wherein 0<w≤0.50.

In an embodiment, the substituted solid zinc oxide is acation-substituted and anion-substituted mixed oxide hydroxide. In afurther embodiment, the cation-substituted and anion-substituted mixedoxide hydroxide has the formulaZn_(1-x)Y_(x)O_(1-w-t)(OH)_(2w)A_((2t/z)), wherein Y is at least onecation substituent, wherein 0<x≤0.50, wherein A is at least one anionsubstituent, 0<w≤0.50, 0<t≤0.50, and z is the charge of the anionsubstituent.

In an embodiment, the cation substituent is selected from the groupconsisting of Mg, Ca, Bi, Ba, Al, Si, Be, Cd, Ni, Co, Sn, and Sr, andany combination thereof.

In an embodiment, the anion substituent is selected from the groupconsisting of CO₃ ²⁻and PO₄ ³⁻, and a combination thereof.

In an embodiment, the anode comprises solid zinc oxide in an amount ofabout 0.2 to 5 volume percent, based on the total volume of the anode.In an embodiment, the anode comprises solid zinc oxide in an amount ofabout 0.3 to 1.5 volume percent, based on the total volume of the anode.In an embodiment, the anode comprises solid zinc oxide in an amount ofabout 0.66 volume percent, based on the total volume of the anode.

In an embodiment, the alkaline electrochemical cell comprises a totalzinc oxide weight percent of about 3.0-8.8%. In an embodiment, thealkaline electrochemical cell comprises a total zinc oxide weightpercent of about 3.0-4.0%, about 4.0-5.0%, about 5.0-6.0%, about6.0-7.0%, about 7.0-8.0%, and about 8.0-9.0%. In an embodiment, thealkaline electrochemical cell comprises a total zinc oxide weightpercent of greater than about 3.0%. In an embodiment, the alkalineelectrochemical cell comprises a total zinc oxide weight percent ofgreater than or equal to about 3.5%, 4.0%, 4.5%, 5.0%, 5.5%, 6.0%, 6.5%,7.0%, 7.5%, 8.0%, and 8.5%. In an embodiment, the alkalineelectrochemical cell comprises a total zinc oxide weight percent ofabout 4.75%.

In an embodiment, the anode comprises an electrolyte concentrationpercent of about 16.0-30.0%. In an embodiment, the anode comprises anelectrolyte concentration percent of about 18.0-22.0%. In an embodiment,the anode comprises an electrolyte concentration percent of less thanabout 22.0%.

In an embodiment, the full cell electrolyte concentration is about26.0-30.0%. In an embodiment, the full cell electrolyte concentration isless than 29.0%.

In an embodiment, the total cell saturation of zinc oxide or zinchydroxide is at least about 40%. In an embodiment, the total cellsaturation of zinc oxide or zinc hydroxide is at least about 40-125%. Inan embodiment, the total cell saturation of zinc oxide or zinc hydroxideis about 40-125%. In an embodiment, the total cell saturation of zincoxide or zinc hydroxide is at least about 40%, 45%, 50%, 55%, 60%, 70%,75%, 80%, 85%, 90%, 95%, 100%, 105%, 110%, 115%, 120%, or 125%.

In an embodiment, the electrochemical cell is a primary cell. In analternate embodiment, the electrochemical cell is a secondary cell.

In an embodiment, the free electrolyte solution comprises potassiumhydroxide (KOH), sodium hydroxide (NaOH), lithium hydroxide (LiOH),magnesium hydroxide (Mg(OH)₂), calcium hydroxide (Ca(OH)₂), magnesiumperchlorate (Mg(ClO₄)₂), magnesium chloride (MgCl₂), or magnesiumbromide (MgBr₂).

In an embodiment, the alkaline electrochemical cell has a specificcapacity or runtime that is greater than that of a similar alkalineelectrochemical cell which lacks the dissolved zinc oxide in the freeelectrolyte. In a further embodiment, the specific capacity or runtimeis from 1% greater to 100% greater, or from 5% greater to 90% greater,or from 10% greater to 80% greater, or from 15% greater to 70% greater,or from 20% greater to 60% greater, or from 25% greater to 50% greater,or from 30% greater to 40% greater.

In an embodiment, wherein the cell has a voltage of 0.1 V-2.0 V, 0.2V-1.9 V, 0.3 V-1.8 V, 0.4 V-1.7 V, 0.5 V-1.6 V, 0.6 V-1.5 V, 0.7 V-1.4V, 0.8 V-1.3 V, 0.9 V-1.2 V, 1.0 V-1.1 V, or is 0.1 V, 0.2 V, 0.3 V, 0.4V, 0.5 V, 0.6 V, 0.7 V, 0.8 V, 0.9 V, 1.0 V, 1.1 V, 1.2 V, 1.3 V, 1.4 V,1.5 V, 1.6 V, 1.7 V, 1.8 V, 1.9 V, or 2.0 V.

The embodiments will be better understood by reference to FIG. 1 whichshows a cylindrical cell 1 in elevational cross-section, with the cellhaving a nail-type or bobbin-type construction and dimensions comparableto a conventional LR6 (AA) size alkaline cell, which is particularlywell-suited to the embodiments. However, it is to be understood thatcells according to the embodiments can have other sizes and shapes, suchas a prismatic or button-type shape; and electrode configurations, asknown in the art. The materials and designs for the components of theelectrochemical cell illustrated in FIG. 1 are for the purposes ofillustration, and other materials and designs may be substituted.Moreover, in certain embodiments, the cathode and anode materials may becoated onto a surface of a separator and/or current collector and rolledto form a “jelly roll” configuration.

In FIG. 1, an electrochemical cell 1 is shown, including a container orcan 10 having a closed bottom end 24, a top end 22 and sidewall 26 therebetween. The closed bottom end 24 includes a terminal cover 20 includinga protrusion. The can 10 has an inner wall 16. In the embodiment, apositive terminal cover 20 is welded or otherwise attached to the bottomend 24. In one embodiment, the terminal cover 20 can be formed withplated steel for example with a protruding nub at its center region.Container 10 can be formed of a metal, such as steel, preferably platedon its interior with nickel, cobalt and/or other metals or alloys, orother materials, possessing sufficient structural properties that arecompatible with the various inputs in an electrochemical cell. A label28 can be formed about the exterior surface of container 10 and can beformed over the peripheral edges of the positive terminal cover 20 andnegative terminal cover 46, so long as the negative terminal cover 46 iselectrically insulated from container 10 and positive terminal 20.

Disposed within the container 10 are a first electrode 18 and secondelectrode 12 with a separator 14 therebetween. First electrode 18 isdisposed within the space defined by separator 14 and closure assembly40 secured to open end 22 of container 10. Closed end 24, sidewall 26,and closure assembly 40 define a cavity in which the electrodes of thecell are housed.

Closure assembly 40 comprises a closure member 42 such as a gasket, acurrent collector 44 and conductive terminal 46 in electrical contactwith current collector 44. Closure member 42 preferably contains apressure relief vent that will allow the closure member to rupture ifthe cell's internal pressure becomes excessive. Closure member 42 can beformed from a polymeric or elastomer material, for example Nylon-6,6 orNylon-6,12, an injection-moldable polymeric blend, such as polypropylenematrix combined with poly(phenylene oxide) or polystyrene, or anothermaterial, such as a metal, provided that the current collector 44 andconductive terminal 46 are electrically insulated from container 10which serves as the current collector for the second electrode 12. Inthe embodiment illustrated, current collector 44 is an elongated nail orbobbin-shaped component. Current collector 44 is made of metal or metalalloys, such as copper or brass, conductively plated metallic or plasticcollectors or the like. Other suitable materials can be utilized.Current collector 44 is inserted through a preferably centrally locatedhole in closure member 42.

First electrode 18 is preferably a negative electrode or anode. Thenegative electrode includes a mixture of zinc (as an active material),an electrically conductive material, solid zinc oxide, and a surfactant.The negative electrode can optionally include other additives, forexample a binder or a gelling agent, and the like. Preferably, thevolume of active material utilized in the negative electrode issufficient to maintain a desired particle-to-particle contact and adesired anode to cathode (A:C) ratio.

Particle-to-particle contact should be maintained during the useful lifeof the battery. If the volume of active material in the negativeelectrode is too low, the cell's voltage may suddenly drop to anunacceptably low value when the cell is powering a device. The voltagedrop is believed to be caused by a loss of continuity in the conductivematrix of the negative electrode. The conductive matrix can be formedfrom undischarged active material particles, conductiveelectrochemically formed oxides, or a combination thereof. A voltagedrop can occur after oxide has started to form, but before a sufficientnetwork is built to bridge between all active material particlespresent.

Zinc suitable for use in the embodiments may be purchased from a numberof different commercial sources under various designations, such as BIA100, BIA 115. Umicore S. A., Brussels, Belgium is an example of a zincsupplier. In a preferred embodiment, the zinc powder generally has 25 to40 percent fines less than 75 μm, and preferably 28 to 38 percent finesless than 75 μm. Generally lower percentages of fines will not allowdesired DSC service to be realized and utilizing a higher percentage offines can lead to increased gassing. A correct zinc alloy is needed inorder to reduce negative electrode gassing in cells and to maintain testservice results.

A surfactant that is either a nonionic or anionic surfactant, or acombination thereof is present in the negative electrode. In anembodiment, the surfactant is a phosphate ester surfactant. It has beenfound that anode resistance is increased during discharge by theaddition of solid zinc oxide alone, but is mitigated by the addition ofthe surfactant. The addition of the surfactant increases the surfacecharge density of the solid zinc oxide and lowers anode resistance asindicated above. Use of a surfactant is believed to aid in forming amore porous discharge product when the surfactant adsorbs on the solidzinc oxide. When the surfactant is anionic, it carries a negative chargeand, in alkaline solution, surfactant adsorbed on the surface of thesolid zinc oxide is believed to change the surface charge density of thesolid zinc oxide particle surfaces. The adsorbed surfactant is believedto cause a repulsive electrostatic interaction between the solid zincoxide particles. It is believed that the surfactant reduces anoderesistance increase caused by the addition of solid zinc oxide becausethe adsorbed surfactant on solid zinc oxide results in enhanced surfacecharge density of solid zinc oxide particle surface. The higher the BETsurface area of solid zinc oxide, the more surfactant can be adsorbed onthe solid zinc oxide surface. In an embodiment, the surfactantconcentration is about 5-50 ppm by weight, relative to the electrodeactive material. In an embodiment, the surfactant concentration is about10-20 ppm.

In an embodiment, the negative electrode comprises solid zinc oxide inan amount from about 0.2 to 5 weight percent, based on the total weightof the negative electrode. In an embodiment, the negative electrodecomprises solid zinc oxide in an amount from about 1 to 4 weightpercent. In a preferred embodiment, the negative electrode comprisessolid zinc oxide in an amount from about 0.3 to 1 weight percent. In amore preferred embodiment, the negative electrode comprises solid zincoxide in an amount of about 0.66 weight percent.

In an embodiment, the solid zinc oxide is substituted, so as to reduceits solubility. In an embodiment, a portion of the zinc in the solidzinc oxide is substituted with another cation. In an embodiment, thesubstituted solid zinc oxide has the formula Zn_(1-x)Y_(x)O, wherein Yis at least one cation substituent, and 0<x≤0.50. In an embodiment, thecation substituent is selected from the group consisting of Mg, Ca, Bi,Ba, Al, Si, Be, Cd, Ni, Co, Sn, and Sr, and any combination thereof. Inan embodiment, x is 0.01-0.40, or 0.02-0.35, or 0.4-0.30, or 0.05-0.25,or 0.10-0.20. In an embodiment, x is ≥0.01, ≥0.02, ≥0.04, ≥0.06, ≥0.08,≥0.10, ≥0.12, ≥0.14, ≥0.16, ≥0.18, ≥0.20, ≥0.25, ≥0.30≥0.35, or ≥0.40.

In an embodiment, a portion of the oxygen in the solid zinc oxide issubstituted with another anion. In an embodiment, the substituted solidzinc oxide has the formula ZnO_(1-w)A_((2w/z)), wherein A is at leastone anion substituent, 0<w≤0.50, and z is the charge of the anionsubstituent. In an embodiment, the anion substituent is selected fromthe group consisting of CO₃ ²⁻and PO₄ ³⁻, and a combination thereof. Inan embodiment, w is 0.01-0.40, or 0.02-0.35, or 0.4-0.30, or 0.05-0.25,or 0.10-0.20. In an embodiment, w is ≥0.01, ≥0.02, ≥0.04, ≥0.06, ≥0.08,≥0.10, ≥0.12, ≥0.14, ≥0.16, ≥0.18, ≥0.20, ≥0.25, ≥0.30≥0.35, or ≥0.40.In an embodiment, the solid zinc oxide comprises a cation substituentand an anion substituent.

The aqueous alkaline electrolyte solution (or simply “aqueouselectrolyte solution”) comprises an alkaline metal hydroxide such aspotassium hydroxide (KOH), sodium hydroxide (NaOH), or the like, ormixtures thereof. Potassium hydroxide is preferred. The alkalineelectrolyte used to form the gelled electrolyte of the negativeelectrode contains the alkaline metal hydroxide in an amount from about16 to about 36 weight percent, for example from about 16 to about 28weight percent, and specifically from about 18 to about 22 weightpercent, or about 20 weight percent, based on the total weight of thealkaline electrolyte solution. In an embodiment, said alkaline metalhydroxide is present in an amount from 16-36 weight percent. In anembodiment, said alkaline metal hydroxide is present in an amountgreater than or equal to 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27,28, 29, 30, 31, 32, 33, 34, 35, or 36 weight percent. In an embodiment,said alkaline metal hydroxide is present in an amount less than or equalto 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32,33, 34, 35, or 36 weight percent. In an embodiment, said alkaline metalhydroxide is present in an amount equal to about 16, 17, 18, 19, 20, 21,22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, or 36 weightpercent.

The aqueous alkaline electrolyte solution also comprises dissolved zincoxide in an amount from about 1.5 to 4 weight percent, based on thetotal weight of the aqueous alkaline electrolyte solution.

A gelling agent is preferably utilized in the negative electrode as iswell known in the art, such as a crosslinked polyacrylic acid, such asCarbopol® 940, which is available from Noveon, Inc. of Cleveland, Ohio,USA. Carboxymethylcellulose, polyacrylamide and sodium polyacrylate areexamples of other gelling agents that are suitable for use in analkaline electrolyte solution. Gelling agents are desirable in order tomaintain a substantially uniform dispersion of zinc and solid zinc oxideparticles in the negative electrode. The amount of gelling agent presentis chosen so that lower rates of electrolyte separation are obtained andanode viscosity in yield stress are not too great which can lead toproblems with anode dispensing.

Dissolved zinc oxide is present in the anode, preferably via dissolutionin the aqueous electrolyte solution, in order to improve plating on thebobbin or nail current collector and to lower negative electrode shelfgassing. The dissolved zinc oxide added is separate and distinct fromthe solid zinc oxide present in the anode composition. Levels ofdissolved zinc oxide in an amount of 3-4 weight percent based on thetotal weight of the negative electrode electrolyte solution arepreferred in one embodiment. In an embodiment, the dissolved zinc oxideis present in the negative electrode electrolyte solution in an amountof greater than 3 weight percent. The soluble or dissolved zinc oxidegenerally has a BET surface area of about 4 m²/g or less measuredutilizing a Tristar 3000 BET specific surface area analyzer fromMicrometrics having a multi-point calibration after the zinc oxide hasbeen degassed for one hour at 150° C.; and a particle size D50 (meandiameter) of about 1 micron, measured using a CILAS particle sizeanalyzer as indicated above.

Other components which may be optionally present within the negativeelectrode include, but are not limited to, gassing inhibitors, organicor inorganic anticorrosive agents, plating agents, binders or othersurfactants. Examples of gassing inhibitors or anticorrosive agents caninclude indium salts, such as indium hydroxide, perfluoroalkyl ammoniumsalts, alkali metal sulfides, etc. In a further embodiment, sodiumsilicate in an amount of about 0.3 weight percent based on the totalweight of the negative electrode electrolyte is preferred in thenegative electrode in order to substantially prevent cell shortingthrough the separator during cell discharge.

The negative electrode can be formed in a number of different ways asknown in the art. For example, the negative electrode components can bedry blended and added to the cell, with alkaline electrolyte being addedseparately or, as in a preferred embodiment, a pre-gelled negativeelectrode process is utilized.

In one embodiment, the zinc and solid zinc oxide powders, and otheroptional powders other than the gelling agent, are combined and mixed.Afterwards, the surfactant is introduced into the mixture containing thezinc and solid zinc oxide. A pre-gel comprising alkaline electrolytesolution, soluble zinc oxide and gelling agent, and optionally otherliquid components, are introduced to the surfactant, zinc and solid zincoxide mixture which are further mixed to obtain a substantiallyhomogenous mixture before addition to the cell. Alternatively, in afurther preferred embodiment, the solid zinc oxide is predispersed in anegative electrode pre-gel comprising the alkaline electrolyte, gellingagent, soluble zinc oxide and other desired liquids, and blended, suchas for about 15 minutes. The solid zinc oxide and surfactant are thenadded and the negative electrode is blended for an additional period oftime, such as about 20 minutes. The amount of gelled electrolyteutilized in the negative electrode is generally from about 25 to about35 weight percent, and for example, about 32 weight percent based on thetotal weight of the negative electrode. Volume percent of the gelledelectrolyte may be about 70% based on the total volume of the negativeelectrode.

In addition to the aqueous alkaline electrolyte absorbed by the gellingagent during the negative electrode manufacturing process, an additionalquantity of an aqueous solution of alkaline metal hydroxide, i.e., “freeelectrolyte,” is added to the cell during the manufacturing process. Thefree electrolyte may be incorporated into the cell by disposing it intothe cavity defined by the positive electrode or negative electrode, orcombinations thereof. The method used to incorporate free electrolyteinto the cell is not critical provided it is in contact with thenegative electrode, positive electrode, and separator. In oneembodiment, free electrolyte is added both prior to addition of thenegative electrode mixture as well as after addition. In one embodiment,about 0.97 grams of 34 weight percent KOH solution is added to an LR6type cell as free electrolyte, with about 0.87 grams added to theseparator lined cavity before the negative electrode is inserted. Theremaining portion of the 34 weight percent KOH solution is injected intothe separator lined cavity after the negative electrode has beeninserted. This free electrolyte solution comprises dissolved zinc oxidein a range of about 0.01-6.0 weight percent. In embodiments, the freeelectrolyte solution comprises dissolved zinc oxide in an amount ofgreater than, less than, or equal to about 0.1, 0.2, 0.3, 0.4, 0.5, 0.6,0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, 2.0,2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8, 2.9, 3.0, 3.1, 3.2, 3.3, 3.4,3.5, 3.6, 3.7, 3.8, 3.9, 4.0, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8,4.9, 5.0, 5.1, 5.2, 5.3, 5.4, 5.5, 5.6, 5.7, 5.8, 5.9, 6.0 weightpercent, or in any range between two of these values. In a preferredembodiment, the free electrolyte solution comprises dissolved zinc oxidein an amount of between about 4.0-6.0 weight percent. The freeelectrolyte solution may be greater than or equal to about 50%, 51%,52%, 53%, 54%, 55%, 56%, 57%, 58%, 59%, 60%, 61%, 62%, 63%, 64%, 65%,66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%,80%, 81%, 82%, 83%, 84%, 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%,94%, 95%, 96%, 97%, 98%, 99%, or 100% saturated with dissolved zincoxide.

Second electrode 12, also referred to herein as the positive electrodeor cathode, includes an electrochemically active material. Electrolyticmanganese dioxide (EMD) is a commonly-used electrochemically activematerial, and is present in an amount generally from about 80 to about92 weight percent and preferably from about 86 to 92 weight percent byweight based on the total weight of the positive electrode, i.e., EMD,conductive material, positive electrode electrolyte and additives,including organic additive(s), if present. The positive electrode isformed by combining and mixing desired components of the electrodefollowed by dispensing a quantity of the mixture into the open end ofthe container and then using a ram to mold the mixture into a solidtubular configuration that defines a cavity within the container inwhich the separator 14 and first electrode 18 are later disposed. Secondelectrode 12 has a ledge 30 and an interior surface 32 as illustrated inFIG. 1. Alternatively, the positive electrode may be formed bypre-forming a plurality of rings from the mixture comprising EMD, andoptionally, additive(s), and then inserting the rings into the containerto form the tubular-shaped second electrode. The cell shown in FIG. 1would typically include 3 or 4 rings.

The positive electrode can include other components such as a conductivematerial, for example graphite, that when mixed with the EMD provides anelectrically conductive matrix substantially throughout the positiveelectrode. Conductive material can be natural, i.e., mined, orsynthetic, i.e., manufactured. In one embodiment, the cells include apositive electrode having an active material or oxide to carbon ratio(O:C ratio) that ranges from about 12 to about 14. Too high of an oxideto carbon ratio decreases the container to cathode resistance, whichaffects the overall cell resistance and can have a potential effect onhigh rate tests, such as the DSC test, or higher cut-off voltages.Furthermore the graphite can be expanded or non-expanded. Suppliers ofgraphite for use in alkaline batteries include Timcal America ofWestlake, Ohio; Superior Graphite Company of Chicago, Ill.; and Lonza,Ltd. of Basel, Switzerland. Conductive material is present generally inan amount from about 5 to about 10 weight percent based on the totalweight of the positive electrode. Too much graphite can reduce EMDinput, and thus cell capacity; too little graphite can increasecontainer to cathode contact resistance and/or bulk cathode resistance.An example of an additional additive is barium sulfate (BaSO₄), which iscommercially available from Bario E. Derivati S.p.A. of Massa, Italy.The barium sulfate is present in an amount generally from about 1 toabout 2 weight percent based on the total weight of the positiveelectrode. Other additives can include, for example, barium acetate,titanium dioxide, binders such as coathylene, and calcium stearate.

In one embodiment, the positive electrode component (such as EMD),conductive material, and barium sulfate, and optionally additive(s) aremixed together to form a homogeneous mixture. During the mixing process,an alkaline electrolyte solution, such as from about 37% to about 40%KOH solution, and optionally including organic additive(s), is evenlydispersed into the mixture thereby insuring a uniform distribution ofthe solution throughout the positive electrode materials. In anembodiment, the alkaline electrolyte solution used to form the cathodecomprises dissolved zinc oxide, in any amount up to and including beingsaturated with dissolved zinc oxide. The mixture is then added to thecontainer and molded utilizing a ram. Moisture within the container andpositive electrode mix before and after molding, and components of themix are preferably optimized to allow quality positive electrodes to bemolded. Mix moisture optimization allows positive electrodes to bemolded with minimal splash and flash due to wet mixes, and with minimalspalling and excessive tool wear due to dry mixes, with optimizationhelping to achieve a desired high cathode weight. Moisture content inthe positive electrode mixture can affect the overall cell electrolytebalance and has an impact on high rate testing.

One of the parameters utilized by cell designers characterizes celldesign as the ratio of one electrode's electrochemical capacity to theopposing electrode's electrochemical capacity, such as the anode (A) tocathode (C) ratio, i.e., A:C ratio. For an LR6 type alkaline primarycell that utilizes zinc in the negative electrode or anode and MnO₂ inthe positive electrode or cathode, the A:C ratio may be greater than1.32:1, such as greater than 1.34:1, and specifically 1.36:1 for impactmolded positive electrodes. The A:C ratio for ring molded positiveelectrodes can be lower, such as about 1.3:1 to about 1.1:1.

Separator 14 is provided in order to separate first electrode 18 fromsecond electrode 12. Separator 14 maintains a physical dielectricseparation of the positive electrode's electrochemically active materialfrom the electrochemically active material of the negative electrode andallows for transport of ions between the electrode materials. Inaddition, the separator acts as a wicking medium for the electrolyte andas a collar that prevents fragmented portions of the negative electrodefrom contacting the top of the positive electrode. Separator 14 can be alayered ion permeable, non-woven fibrous fabric. A typical separatorusually includes two or more layers of paper. Conventional separatorsare usually formed either by pre-forming the separator material into acup-shaped basket that is subsequently inserted under the cavity definedby second electrode 12 and closed end 24 and any positive electrodematerial thereon, or forming a basket during cell assembly by insertingtwo rectangular sheets of separator into the cavity with the materialangularly rotated 90° relative to each other. Conventional pre-formedseparators are typically made up of a sheet of non-woven fabric rolledinto a cylindrical shape that conforms to the inside walls of the secondelectrode and has a closed bottom end.

All of the references cited above, as well as all references citedherein, are incorporated herein by reference in their entireties.

While embodiments have been illustrated and described in detail above,such illustration and description are to be considered illustrative orexemplary and not restrictive. It will be understood that changes andmodifications may be made by those of ordinary skill within the scopeand spirit of the following claims. In particular, embodiments includeany combination of features from different embodiments described aboveand below.

The embodiments are additionally described by way of the followingillustrative non-limiting examples that provide a better understandingof the embodiments and of its many advantages. The following examplesare included to demonstrate preferred embodiments. It should beappreciated by those of skill in the art that the techniques disclosedin the examples which follow represent techniques used in theembodiments to function well in the practice of the embodiments, andthus can be considered to constitute preferred modes for its practice.However, those of skill in the art should, in light of the presentdisclosure, appreciate that many changes can be made in the specificembodiments which are disclosed and still obtain a like or similarresult without departing from the spirit and scope of the embodiments.

DISCUSSION AND EXAMPLES

Discharge of zinc-based batteries involves oxidation of the zinc in theanode, resulting in the formation of zinc oxide, as mentionedpreviously. The zinc oxide reaction product forms a passivation layer,which inhibits the efficient discharge of the remaining zinc. Byaddition of dissolved ZnO (both in the free electrolyte solution and thesolution comprised in the anode) and additional solid ZnO (in theanode), the reaction product is encouraged to precipitate elsewhere.Preventing the passivation layer from coating the anode allows forbetter utilization of the zinc. This results in a substantialimprovement in the runtime on high rate tests, and specifically theDigital Still Camera (DSC) ANSI standard test.

Further, nickel metal hydride (NiMH) chargers are not intended forcharging primary alkaline batteries. The charging can create an abusivecondition which may cause the battery to leak. Specifically, theconstant current charging will cause the decomposition of water,resulting in gas generation and increased internal pressure until thesafety mechanism will vent the electrolyte. Adding a source of zincate(Zn(OH)₄ ²⁻) allows the battery to apply the current at a voltage thatprevents water decomposition, thereby delaying the likelihood ofleakage. This is accomplished by the present embodiments, i.e. bysaturating, or nearly saturating, the electrolyte with dissolved zincoxide and further by adding additional zinc oxide as a solid to theanode formulation. Larger amounts of zinc oxide will further delay thepotential for water decomposition.

While most of the discussion herein refers to zinc oxide being added toelectrodes and electrolyte solutions, other compounds which serve assources of zincate ions may be used instead of, or in addition to, zincoxide. For example, the embodiments described herein may contain Zn(OH)₂in the electrodes and/or electrolyte solutions instead of, or inaddition to, zinc oxide.

Comparison of Surface Passivation in Anodes with and Without Added ZincOxide

Two anodes were prepared, in order to compare the passivation in zincoxide anodes with and without added solid zinc oxide. The compositionsof the control anode and the anode of interest are shown below in Table1.

TABLE 1 Anode and free electrolyte compositions for surface passivationcomparison Control Anode of interest Dissolved ZnO wt % in 28% anode KOH1 3.44 Vol. % solid ZnO 0 2.3 ZnO wt % in surrounding free electrolyte 05.6

Both anodes were discharged, and the surfaces of the discharged anodescan be seen in FIGS. 2A (control anode) and 2B (anode with added zincoxide), after 56 and 76 minutes of the Digital Still Camera (DSC) test,respectively. It is apparent that the discharge reaction and reactionproduct is located preferentially at the anode perimeter near theseparator.

FIGS. 3A and 3B are more highly-magnified images of the reaction zonesfor the control anode and the anode with added zinc oxide, respectively.Under closer magnification, the zinc particles in the control arecovered with ZnO (i.e., are passivated). For the anode with added solidzinc oxide, the ZnO reaction product precipitates at the nucleation siteseeded by the added solid zinc oxide. The zinc surface is therefore leftclean and available for discharge reaction. Higher ZnO levels andpre-saturation increases the probability for the precipitate to occuraway from the zinc surface.

Digital Still Camera (DSC) Test

To test the benefits of the added solid zinc oxide to the anode and ofdissolved zinc oxide to electrolyte solution, a digital still camera(DSC) test was performed on a variety of electrochemical cells. Eachcell was tested to determine the amount of time it took to reduce thevoltage of the cell to 1.05 V. The results are shown in Table 2, below:

TABLE 2 DSC Test Results Solid ZnO DSC Time (vol. % based to 1.05 V CellDissolved ZnO on anode volume) (min) 1 1 wt % based on anode 0 59 weight2 75% saturated based on 0 64 all electrolyte in cell 3 1 wt % based onanode 0.67% 64 weight 4 75% saturated based on 0.67% 94 all electrolytein cell

Adding zinc oxide to the electrolyte solution and to the anode,individually (cells 2 and 3, respectively), are shown to have abeneficial effect compared to cell 1 (containing 1 wt % ZnO in theelectrolyte solution, and no added solid ZnO). However, the combinationof both (in cell 4) shows a drastic increase in performance in the DSCtest. The interaction of both of these added zinc oxides caused a 59%increase in the time the DSC test could be performed on the cellcompared to cell 1. This result would not have been predicted by themodest benefits shown in cells 2 and 3.

Relationship Between Zinc Oxide and Potassium Hydroxide Levels and CellBulging

Corrosion from zinc present in electrodes can cause gassing, whichincreases the internal pressure of a cell. This may cause a cell tobulge and then rupture, during storage or while the cell is in use. Thiscorrosion can also decrease runtime of a cell. Comparisons of cells withrelatively high and low levels of zinc oxide, and high and low levels ofanode potassium hydroxide percentages, were made in order to see howthese relative levels affected the bulge of electrochemical cells. Thetotal zinc oxide saturation percentages in the table below account forboth the zinc oxide actually dissolved in the electrolyte solution, aswell as solid zinc oxide in the anode, which is why the percentage maybe over 100%. These cells were prepared and then stored at 80° C. for 8weeks, to simulate an extended period of aging at room temperature. Thebulge in each of the cells was observed in terms of mils ( 1/1000ths ofan inch), as a stand-in for directly measuring the internal pressure ofthe cells. Results are shown in Table 3:

TABLE 3 Comparison of bulge in aged cells with varying levels of anodeelectrolyte concentration and cell ZnO saturation Total ZnO % SaturationAnode KOH % 80° C. Net Bulge (mils) 65 28 0.9 110 28 3.8 65 20 0.3 11020 1.7

The lower KOH levels resulted in decreased cell bulge, for both thehigher and lower levels of ZnO. Thus, reducing KOH percentage in theanode was found to allow for increased runtime, by permitting increasedlevels of ZnO via mitigation of gassing issues caused by the increase.

Many modifications and other embodiments will come to mind to oneskilled in the art to which these embodiments pertain having the benefitof the teachings presented in the foregoing descriptions and theassociated drawings. Therefore, it is to be understood that theembodiments are not to be limited to the specific embodiments disclosedand that modifications and other embodiments are intended to be includedwithin the scope of the appended claims and list of embodimentsdisclosed herein. Although specific terms are employed herein, they areused in a generic and descriptive sense only and not for purposes oflimitation. For the embodiments described in this application, eachembodiment disclosed herein is contemplated as being applicable to eachof the other disclosed embodiments. For example, while this applicationmostly describes embodiments comprising solid and dissolved zinc oxide,similar embodiments in which all or some of the solid and/or dissolvedzinc oxide is replaced by zinc hydroxide are also considered to bewithin the scope of the embodiments.

What is claimed is:
 1. An alkaline electrochemical cell, comprising: a)a container; and b) an electrode assembly disposed within the containerand comprising a cathode, an anode, a separator located between thecathode and the anode, and a free electrolyte solution; wherein theanode comprises 1) solid zinc, 2) solid particulate zinc oxide or solidparticulate zinc hydroxide in an amount of from about 0.2 to 5 weightpercent, and 3) dissolved zinc oxide or dissolved zinc hydroxide;wherein the free electrolyte solution comprises dissolved zinc oxide ordissolved zinc hydroxide; wherein the anode comprises a gelledelectrolyte, wherein the gelled electrolyte is prepared by combining agelling agent with a first aqueous alkaline electrolyte solution,wherein the first aqueous alkaline electrolyte solution comprises analkaline metal hydroxide electrolyte in an amount less than 30 weightpercent and dissolved zinc oxide in an amount of ≥2.5 weight percent;and wherein the alkaline electrochemical cell is a primary alkalineelectrochemical cell.
 2. The alkaline electrochemical cell of claim 1,wherein the anode comprises solid particulate zinc oxide and dissolvedzinc oxide, and the free electrolyte solution comprises dissolved zincoxide.
 3. The alkaline electrochemical cell of claim 2, wherein the freeelectrolyte solution comprises dissolved zinc oxide in an amount between1.5 and 2.5 weight percent.
 4. The alkaline electrochemical cell ofclaim 1, wherein the cathode comprises a second aqueous alkalineelectrolyte solution, wherein the second aqueous alkaline electrolytesolution comprises an alkaline metal hydroxide electrolyte and dissolvedzinc oxide.
 5. The alkaline electrochemical cell of claim 4, wherein thesecond aqueous alkaline electrolyte solution comprises dissolved zincoxide in an amount of ≥2.5 weight percent.
 6. The alkalineelectrochemical cell of claim 1, wherein the total dissolved zinc oxideweight percent in the electrochemical cell's full cell electrolytesolution is about 1.5-4.5 weight percent.
 7. The alkalineelectrochemical cell of claim 1, wherein the electrochemical cell's fullcell electrolyte is greater than 40% saturated with dissolved zincoxide.
 8. The alkaline electrochemical cell of claim 1, wherein thesolid particulate zinc oxide or solid particulate zinc hydroxide issubstituted and comprises a cation substituent or an anion substituent,wherein the substituted solid particulate zinc oxide or substitutedsolid particulate zinc hydroxide is less soluble than unsubstitutedsolid particulate zinc oxide or unsubstituted solid particulate zinchydroxide.
 9. The alkaline electrochemical cell of claim 8, wherein thesubstituted solid particulate zinc oxide has the formula Zn_(1-x)Y_(x) Oor Zn_(1-x)Y_(x) (OH)₂, wherein Y is at least one cation substituent,and 0<x≤0.50.
 10. The alkaline electrochemical cell of claim 8, whereinthe substituted solid particulate zinc oxide has the formulaZnO_(1-w)A_((2w/z)) or Zn(OH)_(2-w)A_((w/z)), wherein A is at least oneanion substituent, 0<w≤0.50, and z is the charge of the anionsubstituent.
 11. The alkaline electrochemical cell of claim 8, whereinthe substituted solid particulate zinc oxide is a cation-substituted andanion-substituted mixed oxide hydroxide, and has the formulaZn_(1-x)Y_(x) O_(1-w-t)(OH)_(2w)A_((2t/z)), wherein Y is at least onecation substituent, wherein 0<x≤0.50, wherein A, if present, is at leastone anion substituent, 0<w≤0.50, 0≤t≤0.50, and z is the charge of theanion substituent.
 12. The alkaline electrochemical cell of claim 8,wherein the cation substituent, if present, is selected from the groupconsisting of Mg, Ca, Bi, Ba, Al, Si, Be, Cd, Ni, Co, Sn, and Sr, andany combination thereof, and the anion substituent, if present, isselected from the group consisting of CO₃ ²⁻and PO₄ ³⁻, and acombination thereof.
 13. The alkaline electrochemical cell of claim 2,wherein the alkaline electrochemical cell comprises a total zinc oxideweight percent of about 3.0-8.8%.
 14. The alkaline electrochemical cellof claim 2, wherein the alkaline electrochemical cell comprises a totalzinc oxide weight percent of greater than about 7.0%.
 15. The alkalineelectrochemical cell of claim 2, wherein the anode comprises anelectrolyte concentration percent of about 16.0-30.0%.
 16. The alkalineelectrochemical cell of claim 1, wherein the full cell electrolyteconcentration is about 26.0-30.0%.
 17. The alkaline electrochemical cellof claim 1, wherein the total cell saturation of zinc oxide or zinchydroxide is at least about 40%.
 18. The alkaline electrochemical cellof claim 1, wherein the alkaline electrochemical cell has a specificcapacity or runtime that is greater than that of a similar alkalineelectrochemical cell which lacks the dissolved zinc oxide in the freeelectrolyte.
 19. The alkaline electrochemical cell of claim 1, whereinthe cell is a primary cell.